The invention is directed to an electrically controllable permanent magnet load taking or holding device for raising, transporting and stacking ferromagneted parts. The device includes a magnetized permanent magnet centrally arranged in the direction of its smallest dimension in a magnetically conducting iron support member, on which magnet there sits a magnetically conducting compensation, (or complementing) plate having a magnetically conducting bar and magnetically conducting central pole. The device further includes an electrical coil between the compensation plate and the central pole for compensation (displacement) of the magnetic field in the area of the working air gap. This load taking and holding device serves for optimum compensation, i.e., for the most extensive delay free dropping of ferromagnetic thick to thinnest parts having at the same time high holding forces.
There are great difficulties in building permanent magnetic load taking and holding devices, especially for the suspended transfer of sheets in such a manner that they at one time bring about the holding of very thin sheets and at another time of thick sheets during conveying. Then this conveying can only be fulfilled if the holding forces of the load taking and holding device are adjusted to the thickest dimension of the sheet to be encountered in under that even thick sheets can be held safely. On the other hand this means that it is extraordinarily difficult to render these large holding forces inactive in the shortest possible time which is prerequisite for a desired release of the sheet. It is already known to deactivate the permanent magnetic holding force externally by producing an opposing field by an electrical coil which suppresses the permanent magnet flux in a side flux (Schuler/Brinkmann: "Dauermagnet-Werkstaffe und Anwendungen", 1970, page 547 et seq.). With magnetic devices of this type it was possible to stack either only the thinnest sheets or only thick sheets.
The object of the invention is to provide a low taking or holding device with which it is possible to allow sheets to be released independent of their volumes, especially of their thickness, with the least possible delay.